This protocol is based on a study of the interaction setron -paracetamol at 4 different levels of plasma concentrations, by repeating the tests at set intervals, while concentrations of setrons down gradually (half-life of 8 to 10 am ) after a single administration. In addition, the interindividual variability of the effects of paracetamol will be studied, and linking with certain genetic polymorphisms reported by the subjects tested.